A. Field of the Invention
The present invention relates to the field of systems for moving application of a bead of adhesive on a substrate. More specifically, the invention is useful to deposit a thin line of heated glue upon a paper-based substrate to facilitate, e.g. cigarette, cigarette filter, package, carton or case manufacture on an automated production line.
B. Description of the Prior Art
Modern equipment involved in the preparation of packaged consumer goods have made the production of vast quantities of products in short times feasible. For example, today's cigarette machines manufacture cigarettes at a speed of up to 14,000 cigarettes per minute. Several machines working in tandem can now reliably produce in excess of a billion units per day.
Cigarettes are conventionally packaged in packs of 20, although specialty consumer product packs of other goods with varying sizes may contain more or fewer items. On average, then, a single high speed machine can manufacture the equivalent of 700 packs of cigarettes per minute, over 10 packs per second. Other consumer goods are also packaged at high speeds as well (for example, individually wrapped cheese slices and the like). These other goods may be sealed in individual packages for resale in a desired multiple.
With such high speeds of manufacture, down time can be created by a number of factors, and the avoidance of a jammed machine due to mechanical failures is to be avoided as it can cause great expense. One such failure can be caused by inaccurate application of a bead of glue for sealing purposes, causing the packaging or paper wrapper to come undone in the midst of processing. An inaccurately placed bead of glue can cause the final product or a component thereof to have aesthetic defects.
The prior art is replete with attempts to remedy this situation, and attempts to develop nozzles for spraying adhesives and other liquids.
U.S. Pat. No. 3,146,950 issued Sep. 1, 1964 to Lancaster discloses a pressure spraying apparatus with a conventional nozzle. The unit has a hand held nozzle with dual feed lines from liquids at differing temperatures to maintain the temperature of the material (e.g. polyurethane foam) being sprayed.
A demand-served glue nozzle is disclosed in U.S. Pat. No. 3,791,590 in which a glue nozzle is formed with a central bore having a valve stem or plunger. The nozzle exterior has a tapered surface coming to a flat rim point with a convex surface. When the nozzle approaches a workpiece, the plunger releases glue. When the nozzle retracts, the glue supply is shut off and excess glue maintained in the convex surface.
U.S. Pat. No. 4,098,915 discloses a liquid spray head having a needle valve in a spray head. The needle valve is retracted and permits glue to exit from an annular opening surrounding the conical surface of the needle valve.
U.S. Pat. No. 4,249,547 discloses a glue-applying roller with grooves of varying depth to pick up glue from a supply of adhesive and transfer varying amounts of adhesive onto a running web of tipping paper.
U.S. Pat. No. 4,365,585 discloses a spraying device for the application of additives to tobacco. A spraying tip protrudes from a nozzle head which has a plurality of orifices around its periphery. The orifices can contain additive liquid, atomizing liquid, and a cleaning medium. The cleaning medium (e.g. air) is directed to clean the spraying tip.
U.S. Pat. No. 4,562,099 discloses a rotary gravure gummer which is a cylindrical member partly immersed in a bath of adhesive. The adhesive is captured in bores extending through the rotary member and excess is scraped off. The bores deliver the adhesive pattern to a workpiece.
U.S. Pat. No. 4,669,661 discloses the spraying of hot-melt glue through a nozzle with pressurized air. The nozzle is fed by a pneumatically operated extrusion gun.
U.S. Pat. No. 4,895,603 discloses an apparatus and method for cleaning and priming a nozzle assembly. An internal control delivers a rinsing solution to a nozzle, then reprimes the nozzle.
U.S. Pat. No. 5,061,519 discloses an apparatus for patterned gluing. A rotatable shaft supports a plurality of glue nozzles which have ball bearing valves at their tips to release glue on contact with an article.
U.S. Pat. No. 5,221,348 discloses a high pressure manual glue injector with opposed finger grips and a piston which feeds glue to a tapered nozzle upon compression by a user.
U.S. Pat. No. 5,263,608 discloses a method and apparatus for dispensing a constant controlled volume of adhesive. This disclosure, which is incorporated herein in its entirety, describes a method and apparatus for controlling the flow of adhesive onto a moving substrate using a thermal flowmeter. A supply of glue is fed into the nozzle and a spring loaded needle valve, controlled by a supply of pressurized air, is retracted or extended, depending on the amount of glue needed to be extruded onto a passing surface.
U.S. Pat. No. 5,314,559 discloses an apparatus for applying glue to closure stamps for insertion onto packages. A rotatable glue-applying wheel with a recessed radial edge applies a pattern of glue to closure stamp.
U.S. Pat. No. 5,356,050 discloses a mechanism for applying droplets of glue onto sheets. A needle is inserted into a vertical chamber. A droplet of glue forms on the needle, and a blast of air removes the droplet and deposits it on the sheet below.
U.S. Pat. No. 5,553,758 discloses an apparatus for the application of hot melt adhesives using a variety of nozzles. Of particular interest are the nozzle of FIGS. 2A and 2B which are said to be particularly useful for the application of a thin layer of adhesive.
U.S. Pat. No. 5,656,084 discloses a process for coating glue onto pack blanks for the production of hinge-lid packs. A gluing unit having a standard conical nozzle is seen at FIG. 6.
Finally, U.S. Pat. No. 5,720,433 discloses a drawback valve for a glue gun which has a poppet inside a stem which serves as a piston to draw back the glue when the valve is closed to prevent drips.
The above art applies adhesives, but generally in the form of a smear or spray upon the surface, which is not as precise as desired for quality manufacturing procedures. For the glue to transfer to the paper, a form of contact or spray is required. The known prior art results in a smear or spray as noted above. Smears are by their very nature unpredictable and can accumulate along a nozzle in globs, and a spray can result in glue being misapplied and vapor depositing on other portions of the machine, leading to agglomeration of deposits and particles, resulting in a potential for jams and failure. A solution, resulting in an evenly applied bead of adhesive or other liquid is desired.